JP2015217885A - Absorber system for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absorber system for a vehicle which is high in practicality.SOLUTION: An attenuation force generated by an attenuation force generator is usually controlled so as to be differentiated between an elongation time and a contraction time according to a direction of a stroke of a cylinder (S5, S6 and S7), and in the case that a stroke speed of the cylinder is not higher than a set stroke speed (S4), the attenuation force with respect to the elongation/contraction of the cylinder is controlled so as to be selectively switched between an attenuation force (S6) which is set at the elongation time, and an attenuation force (S7) which is set at the contraction time on the basis of whether or not (i) a situation that the steering operability of a vehicle is favorable should be considered as important, or (ii) a situation that a riding comfort of the vehicle is favorable should be considered as important (S8, S9) irrespective of whether or not the cylinder is elongated or contracted.

Description

  The present invention relates to a vehicle absorber system for generating a changeable magnitude of a damping force with respect to a relative motion between an unsprung portion and an unsprung portion.

  In the following patent document, (A) a housing for storing hydraulic fluid, a piston slidably disposed in the housing, a rod having one end connected to the piston and the other end extending from the housing And (C) a hydraulic fluid flow that accompanies the expansion and contraction of the cylinder. A damping force generator that generates a damping force against expansion and contraction of a cylinder by generating resistance, and has a solenoid and generates a damping force having a magnitude corresponding to the current supplied to the solenoid A shock absorber is provided.

JP 2011-007322 A

  Generally, it is desirable that the damping force generated by the shock absorber is different between when the cylinder is extended and when the cylinder is contracted. The shock absorber described in Patent Document 1 is configured to pass through a single damping force generator both when the cylinder is extended and when it is contracted. Therefore, in the vehicle absorber system provided with the shock absorber described in Patent Document 1, in order to make the damping force generated by the damping force generator different at the time of expansion and contraction, the direction of the cylinder stroke is changed. It is necessary to judge. However, when the cylinder expansion / contraction speed is close to 0, it is difficult to determine the cylinder stroke direction. In addition, it is difficult to determine the stroke direction, and the switching between the damping force at the time of expansion and the damping force at the time of contraction is not appropriately performed, thereby deteriorating the steering stability of the vehicle or the riding comfort of the vehicle. There is a fear. That is, it is considered that the practicality of the vehicle absorber system including the damping force generator as described above can be improved by optimizing the damping force against expansion and contraction of the cylinder in the very low speed region. This invention is made | formed in view of such a situation, and makes it a subject to provide the highly practical vehicle absorber system.

  In order to solve the above-described problems, the vehicle absorber system according to the present invention has the following (i) regardless of whether the cylinder is extended or contracted when the stroke speed of the cylinder is equal to or lower than the set stroke speed. Based on whether the vehicle should be focused on good steering stability, or (ii) whether the vehicle should have good ride comfort The damping force for expansion and contraction of the cylinder is controlled so as to be selectively switched between the damping force set at the time of expansion and the damping force set at the time of contraction.

  According to the vehicle absorber system of the present invention, when the stroke speed of the cylinder is in a very low speed region, the operability is improved according to the current position of the vehicle and the intention of the vehicle occupant. It is possible to enhance the comfort. That is, according to the vehicle absorber system of the present invention, it is possible to optimize the damping force against expansion and contraction of the cylinder in the very low speed region. By having such an advantage, the vehicle absorber system of the present invention is highly practical.

Aspects of the Invention

  In the following, some aspects of the invention that can be claimed in the present application (hereinafter sometimes referred to as “claimable invention”) will be exemplified and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is merely for the purpose of facilitating the understanding of the claimable inventions, and is not intended to limit the combinations of the constituent elements constituting those inventions to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which some constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention.

  In each of the following items, the item (1) corresponds to the item 1, and the technical feature described in the item (2) is added to the item 1, the item 2, the item 6 ( The technical feature described in () is added to claim 3, the technical feature described in (7) is added to claim 1 in claim 4, and in claim 4 to (10). The technical feature described in (5) is added to claim 5, the technical feature described in (13) is added to any one of claims 1 to 5, and claim 6 is added. The technical feature described in (14) is added to item 13 to claim 7, and the technical feature described in item (15) is added to any one of claims 1 to 7. Corresponds to claim 8 respectively.

(1) A vehicle having a housing for storing hydraulic fluid, a piston slidably disposed in the housing, a rod having one end connected to the piston and the other end extending from the housing. A cylinder which is arranged so as to be connected to the upper and lower parts of the spring and expands and contracts by relative movement between the upper and lower parts of the spring,
By giving resistance to the flow of hydraulic fluid accompanying the expansion and contraction of the cylinder, a damping force for the expansion and contraction of the cylinder is generated. The solenoid has a magnitude corresponding to the current supplied to the solenoid. A vehicle absorber system comprising: a damping force generator that generates a damping force of: and a control device that controls a damping force against expansion and contraction of the cylinder by controlling a current supplied to the solenoid,
The control device is
When the cylinder is contracted, when the cylinder is contracted, the cylinder is contracted so that the expansion force is a damping force set for the expansion of the cylinder. A stroke direction-based damping force control unit that controls a damping force against expansion and contraction of the cylinder so as to be a damping force when contracting, which is a damping force set to be smaller than the damping force when extending;
When the stroke speed, which is the speed at which the cylinder expands and contracts, is less than or equal to the set stroke speed, regardless of whether the cylinder is extended or contracted, (Ii) whether the vehicle is in a ride-oriented situation, which should be emphasized that the vehicle has a good ride comfort, A steering ride comfort-based damping force control unit for controlling the magnitude of the damping force with respect to expansion and contraction of the cylinder to be selectively switched between the magnitude of the damping force at the time of extension and the magnitude of the damping force at the time of contraction; A vehicle absorber system configured to include the vehicle.

  In the vehicle absorber system described in this section, a single damping force generator is configured to generate a damping force both when the cylinder is extended and when it is contracted, and by the single damping force generator, It is assumed that the damping force when the cylinder is extended and the damping force when the cylinder is contracted are controlled separately. In the vehicle absorber system having such a configuration, it is necessary to determine the direction of the cylinder stroke in order to separately control the damping force when the cylinder is extended and the damping force when the cylinder is contracted. The direction of the stroke is generally determined on the basis of the stroke speed. However, when the stroke speed is close to 0, an error may occur when obtaining the stroke speed. The effect on the damping force due to is large, and the direction of the stroke may be determined in the reverse direction.

  In the vehicle absorber system described in this section, when the stroke speed is in the very low speed range close to 0, the damping force is controlled so as not to depend on the direction of the cylinder stroke, but to emphasize operability or ride comfort. It is supposed to be configured. Therefore, according to the vehicle absorber system in this section, as described above, when it is difficult to determine the direction of the stroke, depending on the current situation of the vehicle and the will of the vehicle occupant Therefore, the damping force can be set to an appropriate magnitude in order to place importance on the maneuverability or ride comfort.

  In the vehicle absorber system described in this section, the extension damping force and the contraction damping force may be set so that the contraction damping force is smaller than the extension damping force. It may be a value determined from the attenuation characteristic or a value determined according to a predetermined control rule. The predetermined control rule includes, for example, a rule that determines the damping force based on the acceleration of the sprung to suppress the vibration of the sprung, or a determination that determines the damping force according to the vehicle speed. Various rules such as rules can be adopted.

The damping force F generated by the damping force generator depends on the relative speed (hereinafter sometimes referred to as “stroke speed”) v _st between the sprung portion and the unsprung portion. Can be expressed as:
F = ζ · v _st ζ: damping coefficient Therefore, when comparing the damping force generated by the damping force generator, the same stroke speed v _st is assumed. In view of this, the magnitude of the damping force in this specification may mean a difference in damping force generation characteristics, specifically, the magnitude of the damping coefficient. It may mean a change in force generation characteristics, specifically a change in damping coefficient.

(2) The steering ride comfort-based damping force control unit includes:
Even when the cylinder is contracted in the situation where emphasis is placed on the stability, the damping force against expansion and contraction of the cylinder is set so that the damping force is the same as the damping force at the time of extension. The vehicle absorber system according to item (1) to be controlled.

  In the aspect described in this section, first, it is determined whether or not it is in a state in which the operability is emphasized. However, the magnitude of the damping force is the same as that during extension. In other words, according to the aspect of this section, it is possible to reliably generate a relatively large damping force and ensure the stability of the vehicle when it is necessary to place importance on the maneuverability.

(3) The steering ride comfort-based damping force control unit includes:
When the steering speed is higher than the set speed, it is assumed that the stability is important, so that the cylinder can be expanded and contracted so that the damping force is the same as the damping force when the cylinder is contracted. The vehicle absorber system according to item (2), wherein the damping force is controlled.

(4) The steering ride comfort-based damping force control unit includes:
When the traveling speed of the vehicle is higher than the set speed, it is assumed that the controllability is important, and even when the cylinder is contracted, the damping force of the cylinder is equal to the damping force when the cylinder is contracted. The vehicle absorber system according to (2) or (3), which controls a damping force against expansion and contraction.

(5) A vehicle equipped with the vehicle absorber system is equipped with a skid prevention system that is a system for suppressing the skid during turning and ensuring the stability of the vehicle.
The steering ride comfort-based damping force control unit,
When the anti-skid system is operating, it is assumed that the stability is important, so that the damping force of the cylinder is the same as the damping force at the time of expansion even when the cylinder is contracted. The vehicle absorber system according to any one of (2) to (4), wherein damping force against expansion and contraction is controlled.

  The modes described in the above three items are modes in which the conditions for determining whether or not the safety-oriented situation is in effect are embodied. According to these aspects, it is possible to appropriately determine whether or not the state is in the state of emphasis on handling.

(6) The steering ride comfort-based damping force control unit includes:
Even when the cylinder is stretched when it is not under the state of emphasis on stability, the damping force against expansion and contraction of the cylinder is set so that the damping force is the same as the damping force at the time of contraction. The vehicle absorber system according to any one of items (2) to (5) to be controlled.

  The mode described in this section is a damping force at the time of contraction with a relatively small damping force except under a situation in which maneuverability is important. That is, according to the aspect described in this section, it is possible to prioritize the ride comfort and improve the operability only when necessary.

(7) The steering ride comfort-based damping force control unit includes:
Controls the damping force against expansion and contraction of the cylinder so that the damping force is the same as the damping force at the time of contraction even when the cylinder is extended when the ride comfort is important. The vehicle absorber system according to (1).

  In the aspect described in this section, first, it is determined whether or not the vehicle is in a state of emphasis on ride comfort. When the vehicle is in a state of emphasis on ride comfort, even when the cylinder is extended, the damping force to be generated is The damping force is the same as that at the time of contraction. That is, according to the aspect of this section, priority is given to a state in which the ride comfort is good, and the stability of the vehicle can be ensured only when necessary.

(8) The steering ride comfort damping force control unit is
When the traveling speed of the vehicle is lower than the set speed, the cylinder is expanded and contracted so that the damping force is the same as the damping force when the cylinder is extended, even when the cylinder is extended, assuming that the ride comfort is important. The vehicle absorber system according to the item (7), which controls a damping force against the vehicle.

(9) The steering ride comfort-based damping force control unit includes:
When the intensity of vibration of the sprung portion is higher than the set level, assuming that the ride comfort is important, so that the damping force is the same as the damping force at the time of contraction even when the cylinder is extended, The vehicle absorber system according to the item (7) or (8), which controls a damping force against expansion and contraction of the cylinder.

  The modes described in the above two items are modes in which the conditions for determining whether or not the vehicle is in a state in which ride comfort is emphasized are embodied. According to these aspects, it is possible to appropriately determine whether or not the ride comfort-oriented situation has been achieved. The “vibration intensity” in the latter mode refers to the degree of vibration intensity. In the latter mode, for example, when the amplitude, the speed of motion of the sprung portion, the acceleration, etc. are relatively high. Therefore, it can be determined that the ride comfort is important. In the latter mode, it is desirable to use the intensity of a specific frequency component (for example, about 8 Hz) that affects the ride comfort among the sprung vibrations.

(10) The steering ride comfort-based damping force control unit includes:
Controls the damping force against expansion and contraction of the cylinder so that the damping force is the same as the damping force at the time of extension even when the cylinder is contracted when the ride comfort is not important. The vehicle absorber system according to any one of (7) to (9).

  The aspect described in this section is an extensional damping force having a relatively large damping force except in a situation where ride comfort is important. In other words, according to the aspect described in this section, it is possible to give priority to the maneuverability and to suppress the deterioration of the ride comfort.

(11) The vehicle absorber system includes a safety control switch that is turned on and off by a vehicle occupant in order to focus on the steering stability of the vehicle.
The steering ride comfort-based damping force control unit,
Even when the cylinder is contracted as if it is in the state of emphasis on the maneuverability when the maneuverability emphasis switch is in the ON state, it has the same magnitude as the damping force at the time of extension. The vehicle absorber system according to (1), wherein a damping force with respect to expansion and contraction of the cylinder is controlled so as to be a damping force.

(12) The vehicle absorber system includes a ride comfort emphasis switch that is turned ON / OFF by a vehicle occupant in order to emphasize the ride comfort of the vehicle,
The steering ride comfort-based damping force control unit,
When the ride emphasis switch is in the ON state, the damping force having the same magnitude as the damping force at the time of contraction is assumed even when the cylinder is extended as being in the ride emphasis situation. The vehicle absorber system according to item (1), wherein damping force against expansion and contraction of the cylinder is controlled so that

  The modes described in the above two items can realize the riding feeling desired by the occupant.

(13) The control device
The cylinder stroke speed is estimated from at least one of (a) the distance between the sprung part between the sprung part and the unsprung part, and (b) the sprung acceleration that is the vertical acceleration of the sprung part. Including a stroke speed estimating unit
The stroke direction dependent damping force control unit,
Any one of the items (1) to (12) configured to determine whether the cylinder is extended or contracted based on the stroke speed estimated by the stroke speed estimation unit. The vehicle absorber system described.

  The stroke speed may be estimated based on a detection value of a stroke sensor or a sprung acceleration sensor. Since the estimated stroke speed includes an error, it is difficult to determine the direction of the stroke when the stroke speed is small. That is, in the aspect described in this section, the control by the vehicle running state-based damping force control unit is particularly effective.

  (14) The vehicle absorber system according to (13), wherein the set stroke speed is set based on a magnitude of an error that may occur when the stroke speed estimation unit estimates the stroke speed.

  In the aspect described in this section, for example, when the set stroke speed is set to a value larger than the maximum error that can occur when the stroke speed is estimated, there is a possibility that the direction of the stroke may be determined in the reverse direction. In addition, it is possible to reliably execute the control by the steering ride comfort dependence control unit.

(15) The damping force generator is
By having a valve mechanism that gives resistance to the flow of the hydraulic fluid by allowing the hydraulic fluid flowing along with the expansion and contraction of the cylinder to pass therethrough, and by applying a force based on the electromagnetic force generated by the solenoid to the valve mechanism Any of (1) to (14) is configured to generate a damping force corresponding to the current supplied to the solenoid by being configured so that the valve opening pressure of the valve mechanism is changed. The absorber system for vehicles as described in any one.

  The mode described in this section is a mode in which the damping force generator is embodied. The “damping force generator” described in this section may have a structure in which a solenoid directly applies a force to the valve body in order to change the valve opening pressure of the valve body. It may have a structure that adjusts the differential pressure between the front side and the rear side.

(16) The damping force generator is
(a) a main flow path through which hydraulic fluid flows when the cylinder expands and contracts, (b) a main valve as the valve mechanism provided in the main flow path, and (c) a bypass provided to bypass the main valve And (d) a pilot chamber that is provided in the bypass path and applies an internal pressure in a direction to close the main valve, and (e) includes the solenoid and is supplied to the solenoid. A pilot valve that changes the internal pressure of the pilot chamber according to the current to be
The vehicle absorber system according to the item (15), wherein the valve opening pressure of the main valve is changed by changing an internal pressure of the pilot chamber by the pilot valve.

  The mode described in this section is a mode in which the damping force generator is further embodied, and the damping force generator is mainly composed of a so-called pilot type electromagnetic valve.

1 is a schematic diagram showing a vehicle suspension system including a vehicle absorber system according to a first embodiment of the claimable invention. It is a schematic sectional drawing of the shock absorber which is a component of the vehicle absorber system of a present Example. It is sectional drawing of the damping force generator shown in FIG. It is a graph which shows the damping characteristic of the damping force generator shown in FIG. It is a flowchart which shows the damping force control program performed by the control apparatus shown in FIG. 6 is a flowchart showing a steering / riding comfort determination subroutine executed in the damping force control program shown in FIG. 5. It is a block diagram which shows the function of the control apparatus shown in FIG. It is a flowchart showing the steering / riding comfort distinction processing subroutine performed in the absorber system for vehicles of the 2nd example.

  Hereinafter, several embodiments of the claimable invention will be described in detail with reference to the drawings as modes for carrying out the claimable invention. In addition to the following examples, the claimable invention is implemented in various modes including various modifications and improvements based on the knowledge of those skilled in the art, including the mode described in the above [Mode of Invention]. can do. Moreover, it is also possible to constitute the modification of the following Example using the technical matter described in the description of each item of [Aspect of the Invention].

First embodiment

[A] Configuration of Vehicle Absorber System FIG. 1 schematically shows a vehicle suspension system 10 including a vehicle absorber system according to a first embodiment of the claimable invention. The suspension system 10 includes four independent suspension type suspension devices 12 corresponding to the front, rear, left, and right wheels 14, respectively. Each of the suspension devices 12 holds the wheels 14 and constitutes a part of the unsprung portion. The suspension lower arm is disposed between the suspension lower arm and the mount portion which is provided on the vehicle body and constitutes a part of the upper portion of the spring. Each of the suspension devices 12 includes a coil spring 16 as a suspension spring and a hydraulic shock absorber 20, which are arranged in parallel with each other between the lower arm and the mount portion. The wheel 14 and the suspension device 12 are generic names, and when it is necessary to clarify which of the four wheels 14 corresponds, as shown in the figure, as a subscript indicating the wheel position, In some cases, FL, FR, RL, and RR are attached to the front wheel, the right front wheel, the left rear wheel, and the right rear wheel.

  As shown in FIG. 2, the hydraulic shock absorber 20 includes a cylinder 22 and a damping force generator 24 as main components. The cylinder 22 includes a housing 30, a piston 32 disposed so as to be movable in the vertical direction inside the housing 30, one end (lower end) connected to the piston 32, and the other end (upper end) at the housing 30. And a rod 34 extending upward. The housing 30 is connected to the lower arm, and the upper end portion of the rod 34 is connected to the mount portion. In other words, when the spring top and the spring bottom move relative to each other in the direction of separation (hereinafter, sometimes referred to as “rebound operation” or “rebound”), the extension and relative movement in the approaching direction (hereinafter referred to as “rebound operation”). , Sometimes referred to as “when bound” or “when bound”).

  The housing 30 includes a bottomed main tube 40, an outer tube 42 attached to the outer periphery thereof, and an inter tube 44 provided between the main tube 40 and the outer tube 42. In general, it has a triple tube structure. The piston 32 is slidably disposed inside the main tube 40. And inside the main tube 40, the rod side chamber 50 and the anti-rod side chamber 52 which are two liquid chambers are divided and formed by the piston 32. In addition, a buffer chamber (also referred to as a “reservoir”) 54 that stores hydraulic fluid is defined between the main tube 40 and the outer tube 42. An annular liquid passage 56 is defined between the inner peripheral surface of the intertube 44 and the outer peripheral surface of the main tube 40. A partition member 58 that partitions the bottom of the anti-rod side chamber 52 is provided at the inner bottom portion of the main tube 40, and a bottom liquid passage 60 is provided between the partition member 58 and the bottom wall of the main tube 40. Is formed.

  In the upper part of the main tube 40, a circulation hole 70 is provided for the circulation of hydraulic fluid between the liquid passage 56 and the rod side chamber 50. Further, a bottom portion circulation hole 72 is provided in a portion near the lower end of the main tube 40 for flowing the working fluid between the buffer chamber 54 and the bottom portion liquid passage 60. An outflow port 74 that allows the working fluid to flow out from the liquid passage 56 to the damping force generator 24 is provided below the intertube 44. The outer tube 42 is provided with an inflow port 76 that allows the working fluid to flow from the damping force generator 24 into the buffer chamber 54.

  As will be described in detail later, the damping force generator 24 is disposed so as to cover the outlet 74 and the inlet 76, flows out of the rod side chamber 52, and passes through the liquid passage 56 to the buffer chamber 54. The hydraulic fluid that flows into the hydraulic fluid is allowed to pass, and the hydraulic fluid has a function of giving resistance to the flow of the hydraulic fluid.

  In the bounding operation of the cylinder 22, as indicated by a solid line arrow in FIG. 2, first, the working fluid flows into the rod side chamber 50 from the non-rod side chamber 52 through the check valve 80 provided in the piston 32. . Since the amount of the hydraulic fluid flowing into the rod side chamber 50 is larger than the volume that increases with the operation of the piston 32 of the rod side chamber 50, the rod side chamber 50 passes through the flow hole 70 and the liquid passage 56, and The hydraulic fluid flows through the damping force generator 24 into the buffer chamber 54. At that time, the damping force generated by the damping force generator 24 against the flow of the hydraulic fluid generates a damping force for the contraction of the cylinder 22, that is, a damping force for the bounce operation.

  On the other hand, during the rebound operation, the hydraulic fluid flows out from the rod side chamber 50 into the buffer chamber 54 through the flow hole 70, the liquid passage 56, and the damping force generator 24, as in the bound operation. At this time, the damping force generated by the damping force generator 24 against the flow of the hydraulic fluid generates a damping force for the extension of the cylinder 22, that is, a damping force for the rebound operation. As shown by the broken arrow in FIG. 2, the counter rod side chamber 52 of the cylinder 22 is passed from the buffer chamber 54 via a check valve 82 provided in the bottom flow hole 60, the bottom liquid passage 60, and the partition member 58. Therefore, the hydraulic fluid flows in.

  Hereinafter, the configuration and operation of the damping force generator 24 will be described with reference to FIG. Since the damping force generator 24 is a known one (for example, described in Japanese Patent Application Laid-Open No. 2011-132959), the description thereof will be simplified. The damping force generator 24 includes a main valve 90 for imparting resistance to the hydraulic fluid passing through the damping force generator 24 and a pilot valve 92 for adjusting the valve opening pressure of the main valve 90 as main components. The main component is a so-called pilot type solenoid valve.

  The main valve 90 and the pilot valve 92 are provided in a housing 100 having a generally covered cylindrical shape. In the housing 100, there is provided a main flow path 102 as a main flow path through which hydraulic fluid flows when the cylinder 22 is expanded and contracted, as indicated by broken arrows in FIG. A main valve 90 is provided in the main flow path 102, and a valve body 104 constituting the main valve 90 is urged in a direction to be seated by a compression coil spring 106. The main valve 90 allows the flow of the hydraulic fluid in the main flow path 102 when it is opened, and provides resistance to the flow of the hydraulic fluid.

  In addition, a bypass passage 110 that bypasses the main valve 90 is provided in the housing 100 as indicated by a solid arrow in FIG. In the bypass passage 110, a fixed orifice 112, a pilot chamber 114, and a pilot valve 92 are provided in this order from the upstream side. The pilot chamber 114 generates an internal pressure in a direction in which the main valve 90 is closed. That is, the main valve 90 has a force acting due to a differential pressure between the hydraulic pressure in the front chamber 116 that is the liquid chamber on the front side of the main valve 90 (the left side of the main valve 90 in FIG. 3) and the hydraulic pressure in the pilot chamber 114. When the urging force of the spring 106 is exceeded, the valve is opened. The fixed orifice 112 is provided so as to penetrate the valve body 104 of the main valve 90, and gives resistance to the flow of hydraulic fluid from the front chamber 116 to the pilot chamber 114.

  The pilot valve 92 includes a movable valve body 120 and a solenoid 122 that generates an electromagnetic force for operating the movable valve body 120 when excited, and is provided downstream of the pilot chamber 114 in the bypass passage 110. Is provided. The movable valve body 120 includes a poppet type valve head 124, and the pilot chamber 114 can be opened and closed by the valve head 124 being attached to and detached from the valve seat 126. The valve movable body 120 is urged by a compression coil spring 128 in a direction in which the valve head 124 is separated. On the other hand, when the solenoid 122 is excited, a biasing force in the direction in which the valve head 124 is seated acts on the valve movable body 120.

  The pilot valve 92 can adjust the opening degree of the pilot chamber 114, in other words, the outflow amount from the pilot chamber 114 to the downstream side, from the above-described configuration. That is, the pilot valve 92 can adjust the valve opening pressure of the main valve 90 by adjusting the hydraulic pressure in the pilot chamber 114. The valve opening pressure of the main valve 90 depends on the magnitude of the current supplied to the solenoid 122 of the pilot valve 92. The larger the current, the smaller the opening of the pilot chamber 114, the higher the hydraulic pressure in the pilot chamber 114, and the higher the valve opening pressure of the main valve 90.

The damping force generator 24 configured as described above has a damping characteristic as shown in FIG. When the relative motion speed v _st (hereinafter sometimes referred to as stroke speed) between the sprung portion and the unsprung portion is low, the main valve 90 is not opened, and the damping force F is applied to the main valve 90. It depends on the resistance to the flow of hydraulic fluid passing through the fixed orifice 112 provided. When the differential pressure between the front chamber 116 and the pilot chamber 114 increases and the main valve 90 is opened, the damping force F depends on the resistance to the flow of hydraulic fluid passing through the main valve 90. is there. As described above, the valve opening pressure of the main valve 90 increases as the current supplied to the solenoid 122 increases.

  In the present suspension system 10, the shock absorber 20 is controlled by a suspension electronic control unit 200 (hereinafter, also referred to as “suspension ECU 200”) as a control device. The ECU 200 is mainly configured by a computer including a CPU, a ROM, a RAM, and the like. The ECU 200 is connected to a driving circuit 202 provided corresponding to the damping force generator 24 of each shock absorber 20 and capable of adjusting the current to the corresponding damping force generator 24. The drive circuits 202 are connected to a battery [BAT] 204, and a current is supplied from the battery 204 to the damping force generator 24 of each shock absorber 20.

  The vehicle includes a vehicle speed sensor [V] 210 for detecting a vehicle traveling speed (hereinafter sometimes abbreviated as “vehicle speed”) and four accelerations for detecting the vertical acceleration of each spring top of the vehicle body corresponding to each wheel 12. A sprung acceleration sensor [Gz] 212, a steering angle sensor [δ] 214 for detecting the operation angle of the steering operation member, and the like are provided, and these are connected to the computer of the ECU 200. Further, the vehicle is provided with a mode selection switch 216 operated by an occupant. By the operation of the mode selection switch 216, (i) a safety-oriented mode that emphasizes safety and (ii) a ride comfort. It is possible to set one of the ride comfort emphasizing modes emphasizing the vehicle to an ON state or an OFF state in which neither is selected. The suspension ECU 200 controls the shock absorber based on signals from these sensors. Incidentally, the character [] is a symbol used when the sensor or the like is shown in the drawing. In addition, the ROM included in the computer of the suspension ECU 200 stores a program related to the control of the shock absorber 20, various data, and the like.

  Further, the vehicle is equipped with a VSC (Vehicle Stability Control) system, which is a system for suppressing the side slip during turning and ensuring the stability of the vehicle, and the VSC-ECU 220 that controls the system is a suspension. The ECU 200 is connected. The suspension ECU 200 can obtain information from the VSC-ECU 220.

[B] Control of damping force (a) Stroke direction-based damping force control In the present suspension system 10, control that normally suppresses vibration of the sprung portion is mainly executed. That is, the supply current to the damping force generator is controlled on the basis of the sprung speed v _s , which is the vertical operating speed of the sprung part, so that a damping force suitable for suppressing the vibration of the sprung part can be obtained. .

Specifically, first, based on the detection value of the sprung acceleration sensor 212 (for example, by the method described in JP-A-9-309315), the stroke speed v _st that is the actual stroke speed of each cylinder 22. Is estimated. Based on the estimated stroke speed _vst , it is determined whether the rebound operation or the bounce operation is performed. Incidentally, the stroke speed may be estimated on the basis of a detection value of a sprung unsprung distance sensor (stroke sensor) that detects a distance between the sprung portion and the unsprung portion. It may be estimated based on both the detection value of the unsprung distance sensor and the detection value of the sprung acceleration sensor.

In the case of the rebound operation, an extension reference current I _E-BASE that is a current supplied to the solenoid 122 serving as a reference during the rebound operation is determined, and the extension reference current I _E-BASE is depending on the sprung velocity v _s estimated from the detection value of the sprung acceleration sensor 212 is corrected. That is, the target supply current I ^* during the rebound operation is determined according to the following equation.
_{^{I * = I E-BASE +}} G E · v s (G E: extension during gain) (1)
In the case in rebound operation, when sprung velocity v _s is upward, the larger the magnitude of the sprung velocity v _s, the target supply current is large, the sprung velocity v _s is downward In this case, the larger the magnitude of the sprung speed v _s is, the smaller it is.

On the other hand, in the case of the bound operation, as in the case of the rebound operation, a contraction reference current I _C-BASE that is a supply current to the solenoid 92 that is a reference for the bound operation is determined. current I _C-BASE is, according to the estimated sprung velocity v _s from the detection value of the sprung acceleration sensor 212 is corrected. That is, the target supply current I ^* during the bound operation is determined according to the following equation.
_{^{I * = I C-BASE +}} G C · v s (G C: systolic gain) (2)
In the case in bound operation, when sprung velocity v _s is downward, the larger the magnitude of the sprung velocity v _s, the target supply current is large, the sprung velocity v _s is upward In this case, the larger the magnitude of the sprung speed v _s is, the smaller it is.

That is, in the present suspension system 10, the damping characteristic when the cylinder 22 is extended and the damping characteristic when the cylinder 22 is contracted are set, and the damping characteristic is switched according to the stroke direction of the cylinder 22. It has become. As can be seen from FIG. 4, the expansion reference current I _E-BASE , the expansion gain G _E , and the contraction reference current I _C-BASE so that the damping force during contraction is smaller than the damping force during expansion. , systolic gain G _C is set.

(B) Steering ride comfort-based damping force control However, when the stroke speed is almost zero, it is difficult to determine the direction of the stroke. As described above, in this suspension system 10, the direction of the stroke is determined based on the stroke speed estimated from the detection value of the sprung acceleration sensor 212, and the stroke speed _vst has an error at the time of estimation. included. Therefore, in the present suspension system 10, it is more difficult to accurately determine the direction of the stroke in the region where the stroke speed is almost zero.

Accordingly, when the estimated stroke speed v _st is smaller than the set stroke speed v _sto , the present suspension system 10 places importance on the operability of the vehicle regardless of the direction of the stroke, Depending on whether the damping characteristic is emphasized or not, it is configured such that the steering ride comfort-based damping force control, which is a control for switching between the damping characteristic at the time of expansion or the damping characteristic at the time of contraction, is executed. The set stroke speed v _sto is set to a value larger than the maximum error that can occur when the stroke speed v _st is estimated. In this suspension system 10, the stroke direction is determined to be opposite. There is no such thing.

In the control ride comfort damping force control, first, it is confirmed whether or not the mode selection switch 216 is operated. If steering stability oriented mode is turned ON, the setting magnitude stroke speed v _sto less than state of the estimated stroke speed v _st is always target supply current during rebound according to the above (1) It is said. On the other hand, if the ride comfort-oriented mode is turned ON, the setting magnitude stroke speed v _sto less than state of the estimated stroke speed v _st is always target supply when bound according to the above (2) Current.

Further, when the mode selection switch 216 is in the OFF state, it is determined whether or not it is in the operability important state. Specifically, when the VSC operation is received from the VSC-ECU 220, the vehicle speed sensor 210 is detected when the steering speed δ ′ estimated from the detected value of the steering angle sensor 214 exceeds the set steering speed δ ₀ ′. any one of the case where the detected vehicle speed V exceeds the set speed V ₀ by but when filled is determined that the steering stability oriented state. And when it is judged that it is in a steerability important state, it is set as the target supply current at the time of rebound according to said (1) Formula. If none of the above three conditions is satisfied, the target supply current at the time of bounding is set according to the above equation (2).

[C] Control Program Control of the vehicle absorber system 10 according to the present embodiment is performed by the ECU 200 executing a damping force control program shown in the flowchart of FIG. 5 for each shock absorber 20. This program is repeatedly executed at a short time pitch (for example, several μsec to several tens μsec).

According to the damping force control program, first, in step 1 (hereinafter, “step” is abbreviated as “S”), the detection value of the sprung acceleration sensor 112 is acquired, and in S2, the sprung speed v _S is calculated. In addition, the stroke speed _vst is estimated in S3. Then, in S4, whether the magnitude of the estimated stroke speed v _st is lower than the set stroke speed v _st0 is determined. When the estimated stroke speed v _st is equal to or higher than the set stroke speed v _st0 , the stroke direction-dependent damping force control is executed in S5 and below, and the estimated stroke speed v _st is lower than the set stroke speed v _st0 In step S8 and subsequent steps, steering ride comfort-based damping force control is executed.

In the stroke direction-dependent damping force control in S5 and below, first, in S5, the direction of the stroke is determined based on the positive / negative of the estimated stroke speed _vst . When the stroke speed _vst is positive and the rebound operation is performed, the target supply current I ^* to the solenoid 122 is determined in S6 according to the above equation (1). On the other hand, when the stroke speed _vst is negative and the bound operation is performed, the target supply current I ^* to the solenoid 122 is determined in S7 according to the above equation (2).

  Further, in the steering ride comfort-based damping force control in S8 and subsequent steps, first, in S8, it is determined whether the emphasis is placed on the steerability or the ride comfort. This is done by executing a subroutine. In this subroutine, the flag value of the importance state flag FL is determined. The flag value of the emphasis state flag FL is set to 0 when it is desired to emphasize the operability, and the flag value is set to 1 when it is desired to focus on the ride comfort.

  In the steering / riding comfort discrimination subroutine, first, in S11, it is determined in the mode selection switch 216 whether or not the riding comfort emphasis mode is in the ON state. The flag value of the importance state flag FL is set to 1. In S12, the mode selection switch 216 determines whether or not the operability priority mode is in the ON state. If it is in the ON state, the flag value of the priority state flag FL is 0 in S17. It is said.

Further, when the mode selection switch 216 is in the OFF state, in S13 to S15, it is determined whether or not a situation in which operability is important is determined. Specifically, in S13, it is determined whether the VSC is operating. In S14, it is determined whether the steering speed δ ′ is higher than the set steering speed δ ₀ ′. In S15, the vehicle speed V is set. whether higher speeds V ₀ is determined. When the VSC is operating, the steering speed δ ′ is higher than the set steering speed δ ₀ ′, or the vehicle speed V is higher than the set speed V ₀ , the operability is emphasized. Since it is necessary, the flag value of the importance state flag FL is set to 0 in S17. On the other hand, if none of the VSC is operating, the steering speed δ ′ is higher than the set steering speed δ ₀ ′, or the vehicle speed V is higher than the set speed V ₀ , the priority state is set in S16. The flag value of the flag FL is set to 1.

In the above subroutine, after the flag value of the importance state flag FL is determined, the flag value of the importance state flag FL is confirmed in S9 of the damping force control program. If the flag value of the importance state flag FL is 0, the target supply current I ^* to the solenoid 122 is determined based on the attenuation characteristic during the rebound operation in S6, and the flag value is 1. In step S7, the target supply current I ^* to the solenoid 122 is determined based on the damping characteristic during the bound operation.

When the target supply current I ^* to the solenoid 122 is determined, a command to the drive circuit 202 is output to supply the determined current to the solenoid 122 in S10. This completes one execution of the damping force control program.

[D] Functional Configuration of Suspension ECU It can be considered that the suspension ECU 200 as a control device that executes the control as described above includes various functional units that perform the various processes described above. Specifically, as shown in FIG. 7, the suspension ECU 200 is based on the sprung speed estimation unit 250 that estimates the sprung speed based on the detected value of the sprung acceleration sensor 212 and the detected value of the sprung acceleration sensor 212. A stroke speed estimation unit 252 that estimates the stroke speed, and a stroke direction determination unit 254 that determines the stroke direction of the cylinder 22 based on the estimated stroke speed. The sprung speed estimation unit 250 includes a part that executes the processes of S1 and S2 of the damping force control program, and the stroke speed estimation unit 252 includes a part that executes the processes of S1 and S3 of the damping force control program. The stroke direction determination unit 254 is configured to include a portion that executes the process of S5 of the damping force control program.

  The suspension ECU 200 has a target supply current determination unit 256 that determines a target supply current to the solenoid 122 based on the attenuation characteristic during the rebound operation or the attenuation characteristic during the bound operation, and the target supply current determination unit. 256 includes a portion that executes the processes of S6 and S7 of the damping force control program. Further, the suspension ECU 20 includes a steering / riding comfort determining unit 258 that determines whether the handling is important or the riding comfort is important. The force control program includes portions for executing the processes of S4 and S8 (operation / riding comfort discrimination subroutine) and S9.

  The vehicle absorber system according to the present embodiment includes a sprung speed estimation unit 250, a stroke speed estimation unit 252, a stroke direction determination unit 254, and a target supply current determination unit 256 according to the stroke direction of the cylinder 22. A stroke direction dependence control unit that controls a damping force against expansion and contraction of the cylinder 22 is configured. In addition, the vehicle absorber system of the present embodiment includes a sprung speed estimation unit 250, a steering / riding comfort determination unit 258, and a target supply current determination unit 256, and does not depend on the stroke direction of the cylinder 22, and Based on whether or not the importance of good steering stability is present, the damping force for expansion and contraction of the cylinder 22 is set between the damping force set during expansion and the damping force set during contraction. A steering ride comfort reliance control unit that selectively switches with is configured.

Second embodiment

  As described above, the vehicle absorber system according to the first embodiment is based on whether or not the steering ride comfort reliance control unit is under a situation where importance should be placed on good steering stability of the vehicle. The damping force for expansion and contraction of the cylinder 22 is configured to be selectively switched between a damping force set at the time of expansion and a damping force set at the time of contraction. In contrast, in the vehicle absorber system of the second embodiment, the cylinder 22 is based on whether or not the control ride comfort control unit is in a situation where importance should be placed on good ride comfort of the vehicle. The damping force with respect to expansion / contraction is selectively switched between the damping force set at the time of expansion and the damping force set at the time of contraction.

  The vehicle absorber system of the second embodiment differs from the vehicle absorber system of the first embodiment only in the steering / riding comfort determination subroutine executed in the damping force control program shown in FIG. For the vehicle absorber system according to the second embodiment, only the control / riding comfort discrimination processing subroutine will be described. FIG. 8 shows a flowchart of a steering / riding comfort determination subroutine executed in the vehicle absorber system of the second embodiment.

  In the steering / riding comfort discrimination subroutine in the present embodiment, as in the first embodiment, first, in S21 and S22, it is confirmed whether or not the mode selection switch 216 is in the ON state, and the steering emphasis mode is selected. Is set to the ON state, the flag value of the priority state flag FL is set to 0 in S25, and when the ride comfort priority mode is set to the ON state, the flag of the priority state flag FL is set to S26. The value is set to 1.

If the mode selection switch 216 is in the OFF state, in S23 and S24, it is determined whether or not the ride comfort is emphasized. Specifically, in S23, the sprung acceleration sensor detects the sprung acceleration detected by 210, and a component in a frequency range (about 8 Hz) that greatly affects the riding comfort of the vehicle is extracted. Then, the acquired amplitude a of the extracted frequency component, whether the amplitude a of the specific frequency component is greater than the set amplitude a ₁ is determined. Then, the amplitude a of the specific frequency component is larger than the set amplitude a _1, as the under ride emphasis situation, in S26, the flag value of the focus state flag FL is set to 1.

Also, if the amplitude a of the specific frequency component is set amplitude a ₁ or less, in S24, whether the vehicle speed V is lower than the set speed V ₁ is determined. When the vehicle speed V is lower than the set speed V ₁ as under ride emphasis situation, in S26, the flag value of the focus state flag FL is set to 1. That is, in the damping force control program, the target supply current to the solenoid 122 is determined based on the damping characteristic during the bounding operation.

  On the other hand, when it is determined in S23 and S24 that the vehicle is not in a state of emphasis on riding comfort, the flag value of the importance state flag FL is set to 0 in S25. That is, in the damping force control program, the target supply current to the solenoid 122 is determined based on the damping characteristic during the rebound operation.

10: Vehicle suspension system 12: Suspension device 14: Wheel 16: Suspension spring 20: Hydraulic shock absorber 22: Cylinder 24: Damping force generator 30: Housing 32: Piston 34: Rod 4 90: Main valve 92: Pilot valve DESCRIPTION OF SYMBOLS 100: Housing 102: Main flow path 104: Valve body 106: Compression coil spring 110: Bypass path 112: Fixed orifice 114: Pilot chamber 116: Front chamber 120: Valve movable body 122: Solenoid 200: Suspension electronic control unit [suspension ECU] [Control Device] 210: Vehicle speed sensor [V] 212: Sprung acceleration sensor [Gz] 214: Steering angle sensor [δ] 216: Mode selection switch [Sw] [Operation control priority switch, ride comfort priority Switch] 220: VSC-ECU 250: sprung speed estimating section 252: Stroke speed estimating section 254: stroke direction judging section 256: target electric current determining section 258: steering stability, ride comfort discrimination processing unit

Claims (8)

A spring top of a vehicle having a housing for storing hydraulic fluid, a piston slidably disposed in the housing, a rod having one end connected to the piston and the other end extending from the housing And a cylinder which is arranged so as to be connected to the unsprung part and expands and contracts by relative movement between the unsprung part and the unsprung part,
By giving resistance to the flow of hydraulic fluid accompanying the expansion and contraction of the cylinder, a damping force for the expansion and contraction of the cylinder is generated. The solenoid has a magnitude corresponding to the current supplied to the solenoid. A vehicle absorber system comprising: a damping force generator that generates a damping force of: and a control device that controls a damping force against expansion and contraction of the cylinder by controlling a current supplied to the solenoid,
The control device is
When the cylinder is contracted, when the cylinder is contracted, the cylinder is contracted so that the expansion force is a damping force set for the expansion of the cylinder. A stroke direction-based damping force control unit that controls a damping force against expansion and contraction of the cylinder so as to be a damping force when contracting, which is a damping force set to be smaller than the damping force when extending;
When the stroke speed, which is the speed at which the cylinder expands and contracts, is less than or equal to the set stroke speed, regardless of whether the cylinder is extended or contracted, (Ii) whether the vehicle is in a ride-oriented situation, which should be emphasized that the vehicle has a good ride comfort, A steering ride comfort-based damping force control unit for controlling the magnitude of the damping force with respect to expansion and contraction of the cylinder to be selectively switched between the magnitude of the damping force at the time of extension and the magnitude of the damping force at the time of contraction; A vehicle absorber system configured to include the vehicle. The steering ride comfort-based damping force control unit,
Even when the cylinder is contracted in the situation where emphasis is placed on the stability, the damping force against expansion and contraction of the cylinder is set so that the damping force is the same as the damping force at the time of extension. The vehicle absorber system according to claim 1 to be controlled. The steering ride comfort-based damping force control unit,
Even when the cylinder is stretched when it is not under the state of emphasis on stability, the damping force against expansion and contraction of the cylinder is set so that the damping force is the same as the damping force at the time of contraction. The vehicle absorber system according to claim 2 to be controlled. The steering ride comfort-based damping force control unit,
Controls the damping force against expansion and contraction of the cylinder so that the damping force is the same as the damping force at the time of contraction even when the cylinder is extended when the ride comfort is important. The vehicle absorber system according to claim 1. The steering ride comfort-based damping force control unit,
Controls the damping force against expansion and contraction of the cylinder so that the damping force is the same as the damping force at the time of extension even when the cylinder is contracted when the ride comfort is not important. The vehicle absorber system according to claim 4. The control device is
The cylinder stroke speed is estimated from at least one of (a) the distance between the sprung part between the sprung part and the unsprung part, and (b) the sprung acceleration that is the vertical acceleration of the sprung part. Including a stroke speed estimating unit
The stroke direction dependent damping force control unit,
6. The apparatus according to claim 1, configured to determine whether the cylinder is expanding or contracting based on a stroke speed estimated by the stroke speed estimating unit. 7. Absorber system for vehicles.   The vehicle absorber system according to claim 6, wherein the set stroke speed is set based on a magnitude of an error that may occur when the stroke speed estimation unit estimates the stroke speed. The damping force generator is
By having a valve mechanism that gives resistance to the flow of the hydraulic fluid by allowing the hydraulic fluid flowing along with the expansion and contraction of the cylinder to pass therethrough, and by applying a force based on the electromagnetic force generated by the solenoid to the valve mechanism 8. The system according to claim 1, wherein a damping force corresponding to a current supplied to the solenoid is generated by changing the valve opening pressure of the valve mechanism. The vehicle absorber system described in 1.

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